Syntactic TheoryIntroduction

Yi Zhang & Antske Fokkens

Department of Computational LinguisticsSaarland University

October 15, 2009

Syntax: What does it mean?

We can view syntax/syntactic theory in a number of ways, twoof which are the following:

I Psychological way/model: syntactic structures correspondto what is in the heads of speakers and hearers

I Computational way/model: syntactic structures are formalobjects which can be mathematically treated/manipulated

Syntactic Analysis

I Focus on collection of words and rules with which wegenerate

I strings of those words (weak generative power)I structures which license strings of those words (strong

generative power)I Syntax attempts to capture the nature of those rules:

1. Colorless green ideas sleep furiously2. *Furiously sleep ideas green colorless.3. *Sally talk to man.4. Sally talks to a man.

I What generalizations are needed to capture the differencebetween grammatical and ungrammatical sentences?

Why is the Study of Syntax Relevant?

[Sag, Watson and Bender, 2003]

I A window on the structure of the mindI Innateness of the language faculty (Chomsky)

I Universal GrammarI A window on the mind’s activity

I Cognitive processI Ambiguity management

I Natural language technologiesI ParsingI GenerationI Grammar checking

Why is the Study of Syntax Relevant?

[Sag, Watson and Bender, 2003]

I A window on the structure of the mindI Innateness of the language faculty (Chomsky)

I Universal GrammarI A window on the mind’s activity

I Cognitive processI Ambiguity management

I Natural language technologiesI ParsingI GenerationI Grammar checking

Why is the Study of Syntax Relevant?

[Sag, Watson and Bender, 2003]

I A window on the structure of the mindI Innateness of the language faculty (Chomsky)

I Universal GrammarI A window on the mind’s activity

I Cognitive processI Ambiguity management

I Natural language technologiesI ParsingI GenerationI Grammar checking

Why is the Study of Syntax Relevant?

[Sag, Watson and Bender, 2003]

I A window on the structure of the mindI Innateness of the language faculty (Chomsky)

I Universal GrammarI A window on the mind’s activity

I Cognitive processI Ambiguity management

I Natural language technologiesI ParsingI GenerationI Grammar checking

Why is the Study of Syntax Relevant?

[Sag, Watson and Bender, 2003]

I A window on the structure of the mindI Innateness of the language faculty (Chomsky)

I Universal GrammarI A window on the mind’s activity

I Cognitive processI Ambiguity management

I Natural language technologiesI ParsingI GenerationI Grammar checking

Why is the Study of Syntax Relevant?

[Sag, Watson and Bender, 2003]

I A window on the structure of the mindI Innateness of the language faculty (Chomsky)

I Universal GrammarI A window on the mind’s activity

I Cognitive processI Ambiguity management

I Natural language technologiesI ParsingI GenerationI Grammar checking

Two Conceptions of Grammar

Prescriptive grammar

Consists of admonitions not to use certain forms orconstructions that are common in everyday speech:

I Never split an infinitive.I A preposition is a bad word to end a sentence with.

Human language is a phenomenon amenable to scientificinvestigation, rather than something to be regulated by thedecrees of authorities

Natural phenomena can NOT be legislated!

Two Conceptions of Grammar

Prescriptive grammar

Consists of admonitions not to use certain forms orconstructions that are common in everyday speech:

I Never split an infinitive.I A preposition is a bad word to end a sentence with.

Human language is a phenomenon amenable to scientificinvestigation, rather than something to be regulated by thedecrees of authorities

Natural phenomena can NOT be legislated!

Two Conceptions of Grammar

Prescriptive grammar

Consists of admonitions not to use certain forms orconstructions that are common in everyday speech:

I Never split an infinitive.I A preposition is a bad word to end a sentence with.

Human language is a phenomenon amenable to scientificinvestigation, rather than something to be regulated by thedecrees of authorities

Natural phenomena can NOT be legislated!

Two Conceptions of Grammar

Prescriptive grammar

Consists of admonitions not to use certain forms orconstructions that are common in everyday speech:

I Never split an infinitive.I A preposition is a bad word to end a sentence with.

Human language is a phenomenon amenable to scientificinvestigation, rather than something to be regulated by thedecrees of authorities

Natural phenomena can NOT be legislated!

Two Conceptions of Grammar

Prescriptive grammar

Consists of admonitions not to use certain forms orconstructions that are common in everyday speech:

I Never split an infinitive.I A preposition is a bad word to end a sentence with.

Human language is a phenomenon amenable to scientificinvestigation, rather than something to be regulated by thedecrees of authorities

Natural phenomena can NOT be legislated!

Two Conceptions of Grammar

Descriptive grammar

I Observes language and creates conceptual categories forit without establishing rules of language

I Consults intuitions of native speakers on what soundsgood

1. They saw Pat with Chris.2. They saw Pat and Chris.3. Who did they see Pat with?4. * Who did they see Pat and?

Syntax vs. Grammar

Two terms are in many cases used interchangeably, but

Syntax contrasts with semantics, morphology and phonology,and focus on the way words are put together into phrases, andphrases into sentences, although the boundaries are notalways sharp.

Grammar Formalisms

Computational grammar formalisms share several propertiesI Descriptive adequacyI Precise encodingI Constrained formalism

Descriptive Adequacy

Some researchers try to explain the underlying mechanisms,but we are most concerned with being able to describelinguistic phenomena

I Provide a structural description for every well-formedsentence

I Give us an accurate encoding of a languageI Give us broad-coverage, i.e., can (try to) describe all of a

language

Precise Encoding

Mathematical Formalism: formal way to generate sets ofstrings or structures

Precisely define:I elementary structuresI ways of combining those structures

Such an emphasis on mathematical precision makes thesegrammar formalism more easily implementable

Constrained Formalism

A formalism must be constrained:

I Linguistic motivation: limits the scope of the theory ofgrammar

I Computational motivation: allows us to define efficientprocessing models

Simplistic Syntactic Theory Example IList as grammars

A grammar consists of a list of all the well-formedsentences in the language

I Some sentences go on and on.

I Some sentences go on and on and on.

I Some sentences go on and on and on and on.

I . . .

I Grammar G1 is defined by the language L it self, as a set ofstrings G1 = {si |si ∈ L }

I Weak expressive power: cannot enumerate all possiblesentences in a language

I No (useful) structure

I No generalization over linguistic phenomena

Simplistic Syntactic Theory Example IList as grammars

A grammar consists of a list of all the well-formedsentences in the language

I Some sentences go on and on.

I Some sentences go on and on and on.

I Some sentences go on and on and on and on.

I . . .

I Grammar G1 is defined by the language L it self, as a set ofstrings G1 = {si |si ∈ L }

I Weak expressive power: cannot enumerate all possiblesentences in a language

I No (useful) structure

I No generalization over linguistic phenomena

Simplistic Syntactic Theory Example IList as grammars

A grammar consists of a list of all the well-formedsentences in the language

I Some sentences go on and on.

I Some sentences go on and on and on.

I Some sentences go on and on and on and on.

I . . .

I Grammar G1 is defined by the language L it self, as a set ofstrings G1 = {si |si ∈ L }

I Weak expressive power: cannot enumerate all possiblesentences in a language

I No (useful) structure

I No generalization over linguistic phenomena

Simplistic Syntactic Theory Example IIRegular Expressions

Regular Expressions, i.e. patterns making use ofKleene star (and Kleene plus), parentheses foroptionality, and the vertical bar for alternatives, can beused to describe grammars

I G2: Some sentences go on [and on]+.

I Insufficient description power to capture generalizations

Syntactic Theories to be Reviewed

In this course, we will introduce the following linguisticframeworks

I Chomskyan Transformational Tradition & MinimalismI Dependency GrammarI Tree Adjoining GrammarI Lexical Functional GrammarI Head-Driven Phrase Structure Grammar

With particular focus on the LFG and HPSG

Organizational Matters

I Time: Tuesday 16:15 - 17:45, Thursday 14:15 - 15:45I Location: Seminar Room, C72I Office hours: Thursday 13:00 - 14:00 (after email contact)I Credit Points: 6 CPI Course Homepage:

http://www.coli.uni-saarland.de/courses/syntactic-theory-09/

Lectures, Exercises, and Exam

I Regular attendance of the lectures are requiredI Exercises needs to be submitted in, and will be correctedI One must “pass” at least half of the exercises to be

qualified for the final exam